Anion Effect on CO₂ Electrochemical Reduction in Acidic Media

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• The carbon dioxide electroreduction reaction (CO2RR) converts renewable electricity into valuable chemicals.
• Acidic CO2RR selectivity is limited by the hydrogen evolution reaction, with anion effects being underexplored.
• Understanding anion influence is crucial for optimizing CO2RR performance.

Purpose of the Study:

• To systematically investigate the effect of common anions (Cl-, SO4^2-, H2PO4^-) on acidic CO2RR.
• To elucidate the role of anions in influencing selectivity towards C2+ products.
• To identify effective anion electrolyte engineering strategies for enhanced CO2RR.

Main Methods:

• Theoretical calculations to study anion-induced surface charge effects on copper.
• Electrochemical evaluations of copper and silver catalysts in different acidic electrolytes.
• In situ Raman spectroscopy to probe CO intermediate adsorption.

Main Results:

• Chloride ions (Cl-) induce negative surface charge on copper, enhancing C-C coupling.
• Copper catalysts in Cl--containing electrolytes show superior C2+ selectivity.
• A peak C2+ Faradaic efficiency of 82% was achieved at 300 mA cm^-2.
• The promotional effect of Cl- was also observed on silver catalysts.
• In situ Raman spectroscopy confirmed enhanced CO intermediate adsorption by Cl-.

Conclusions:

• Anion choice is a critical factor for controlling selectivity in acidic CO2RR.
• Chloride ions effectively promote C-C coupling and C2+ product formation.
• Anion electrolyte engineering offers a viable strategy to enhance CO2RR performance.